INSECTS. 371 



naoious; and some few are furaislied with special weapons 

 for fighting with their rivals. But the law of battle does 

 not prevail nearly so widely with insects as with the higher 

 animals. Hence it probably arises that it is in only a 

 few cases that the males have been rendered larger and 

 stronger than the females. On the contrary, they are 

 usually smaller, so that they may be developed within a 

 shorter time, to be ready in large numbers for the emerg- 

 ence of the females^ 



CJn two families of the Homoptera and in three of the 

 Orthoptera, the males alone possess sound-producing organs 

 in an efficient state. These are used incessantly during the 

 breeding-season, not only for calling the females, but ap- 

 parently for charming or exciting them in rivalry with 

 other males. Xo one who admits the agency of selection 

 of any kind, will, after reading the above discussion, dis- 

 pute that these musical instruments have been acquired 

 through sexual selection J In four other orders the mem- 

 bers of one sex, or more commonly of both sexes, are pro- 

 vided with organs for producing various sounds, which ap- 

 parently serve merely as call-notes. When both sexes are 

 thus provided the individuals which were able to make the 

 loudest or most continuous noise would gain partners before 

 those which were less noisy, so that their organs have proba- 

 bly been gained through sexual selection. It is instructive 

 to reflect on the wonderful diversity of the means for pro- 

 ducing sound, possessed by the males alone, or by both 

 sexes in no less than six orders. We thus learn how effectual 

 sexual selection has been in leading to modifications which 

 sometimes, as with the Homoptera, relate to important 

 parts of the organization. 



From the reasons assigned in the last chapter, it is proba- 

 ble that the great horns possessed by the males of many 

 Lamellicom, and some other beetles, have been acquired as 

 ornaments. From the small size of insects we are apt to 

 undervalue their appearance. If we could imagine a male 

 Chalcosoma(seefig. 16), with its polished bronzed coat of mail 

 and its vast complex horns, magnified to the size of a 

 horse, or even of a dog, it would be one of the most impos- 

 ing animals in the world. 



The coloring of insects is a complex and obscure subject. 

 When the male differs slightly from the female, and 

 neither are brilliantly colored, it is probable that the sexes 



